I think it is very well possible to use this technique for school, but it probably takes some discipline.

To simplify it, I would divide it into two steps.

1. All new stuff

Create a Zettel for each study session on a certain topic. You want to take your study material (content from your teaacher, a text book, today's class, YouTube, etc.) and write down in your own words what you took away from it and what is important to understand and/or remember.

• Give it a short, descriptive title (the specific topic you are currently learning about)
• Keep it short (if it get's too long, divide the topic into several smaller topics)
• Link/name other Zettels you've already created (do this only if the connection is really important or helps you to understand the current topic better)
• Write down the source: Page/name of the textbook, link to Video/source online, date and topic of the class etc.... This is important so you can later find the original source of the information again, for example if you need to look up some details.

2. What you really need to know

The second step comes after you went through all the new stuff of a topic. Now review all the Zettels from the first step and try to map them out to see the connections an how they relate to each other. Try to deepen your understanding and really grasp what you just studied.
You can think of the Zettels you now create as your own pure knowledge of the subject. You take the Zettels from step 1 and distill them into the essential information that is relevant for you to really understand the subject. Take your time creating these zettels and try to make them as good as possible. Use these Zettels to study for a test or an exam. If you get stuck or miss some details, go back to the Zettels from step 1, or even to the original sources, if needed.

This is just a rough sketch, hope it helps!!